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Sep 21, 2013
09/13

by
Eugene Demler; Fei Zhou

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We study superfluid and Mott insulator phases of cold spin-1 Bose atoms with antiferromagnetic interactions in an optical lattice, including a usual polar condensate phase, a condensate of singlet pairs, a crystal spin nematic phase, and a spin singlet crystal phase. We suggest a possibility of exotic fractionalized phases of spinor BEC and discuss them in the language of topological defect condensation and $Z_2$ lattice gauge theory.

Source: http://arxiv.org/abs/cond-mat/0104409v2

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Sep 22, 2013
09/13

by
Yuval Oreg; Eugene Demler

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We discuss the destruction of superconductivity in quasi-one-dimensional systems due to the interplay between disorder and Coulomb repulsion. We argue that to understand the behavior of the system one has to study both fermionic and bosonic mechanisms of suppression of superconductivity. The former describes reduction in the mean field critical temperature $T_c$, while the latter refers to thermal and quantum fluctuations in the order parameter. A change in parameters such as wire width and...

Source: http://arxiv.org/abs/cond-mat/0106645v2

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Jul 20, 2013
07/13

by
David Pekker; Eugene Demler

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Tunability of effective two body interactions near Feshbach resonances is a powerful experimental tool in systems of ultracold atoms. It has been used to explore a variety of intriguing phenomena in recent experiments. However not all of the many-body properties of such systems can be understood in terms of effective models with contact interaction given by the scattering length of the two particles in vacuum. For example, when a two component Fermi mixture is quenched to the BEC side of the...

Source: http://arxiv.org/abs/1107.3930v1

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Sep 18, 2013
09/13

by
Adilet Imambekov; Eugene Demler

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We consider a one dimensional interacting bose-fermi mixture with equal masses of bosons and fermions, and with equal and repulsive interactions between bose-fermi and bose-bose particles. Such a system can be realized in experiments with ultracold boson and fermion isotopes in optical lattices. We use the Bethe-ansatz technique to find the ground state energy at zero temperature for any value of interaction strength and density ratio between bosons and fermions. We prove that the mixture is...

Source: http://arxiv.org/abs/cond-mat/0505632v2

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Sep 18, 2013
09/13

by
Eugene Demler; Andrei Maltsev

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We investigate theoretically soliton excitations and dynamics of their formation in strongly correlated systems of ultracold bosonic atoms in two and three dimensional optical lattices. We derive equations of nonlinear hydrodynamics in the regime of strong interactions and incommensurate fillings, when atoms can be treated as hard core bosons. When parameters change in one direction only we obtain Korteweg-de Vries type equation away from half-filling and modified KdV equation at half-filling....

Source: http://arxiv.org/abs/1102.3349v1

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Sep 20, 2013
09/13

by
Gergely Zarand; Eugene Demler

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We study quantum phase transitions in the Bose-Fermi Kondo problem, where a local spin is coupled to independent bosonic and fermionic degrees of freedom. Applying a second order expansion in the anomalous dimension of the Bose field we analyze the various non-trivial fixed points of this model. We show that anisotropy in the couplings is relevant at the SU(2) invariant non Fermi liquid fixed points studied earlier and thus the quantum phase transition is usually governed by XY or Ising-type...

Source: http://arxiv.org/abs/cond-mat/0204118v2

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1.0

Jun 28, 2018
06/18

by
Fabian Grusdt; Eugene Demler

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The Fr\"ohlich polaron model describes a ubiquitous class of problems concerned with understanding properties of a single mobile particle interacting with a bosonic reservoir. Originally introduced in the context of electrons interacting with phonons in crystals, this model found applications in such diverse areas as strongly correlated electron systems, quantum information, and high energy physics. In the last few years this model has been applied to describe impurity atoms immersed in...

Topics: Other Condensed Matter, Quantum Gases, Condensed Matter

Source: http://arxiv.org/abs/1510.04934

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Sep 21, 2013
09/13

by
Gil Refael; Eugene Demler

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The superfluid-insulator transition of bosons is strongly modified by the presence of Fermions. Through an imaginary-time path integral approach, we derive the self-consistent mean-field transition line, and account for both the static and the dynamic screening effects of the fermions. We find that an effect akin to the fermionic orthogonality catastrophe, arising from the fermionic screening fluctuations, suppresses superfluidity. We analyze this effect for various mixture parameters and...

Source: http://arxiv.org/abs/0712.1828v1

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Sep 23, 2013
09/13

by
Mehrtash Babadi; Eugene Demler

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We study the in-plane and out-of-plane density ordering instabilities of quasi-two-dimensional fermionic polar molecules in single-layer and multi-layer configurations. We locate the soft modes by evaluating linear response functions within the conserving time-dependent Hartree-Fock (TDHF). The short-range exchange effects are taken into account by solving the Bethe-Salpeter integral equation numerically. An instability phase diagram is calculated for both single-layer and multi-layer systems...

Source: http://arxiv.org/abs/1109.3755v2

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Sep 21, 2013
09/13

by
Mehrtash Babadi; Eugene Demler

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We theoretically analyze a quasi-two-dimensional system of fermionic polar molecules in a harmonic transverse confining potential. The renormalized energy bands are calculated by solving the Hartree-Fock equation numerically for various trap and dipolar interaction strengths. The inter-subband excitations of the system are studied in the conserving time-dependent Hartree-Fock (TDHF) approximation from the perspective of lattice modulation spectroscopy experiments. We find that the excitation...

Source: http://arxiv.org/abs/1106.4345v1

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Sep 23, 2013
09/13

by
Adilet Imambekov; Eugene Demler

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We consider one dimensional interacting bose-fermi mixture with equal masses of bosons and fermions, and with equal and repulsive interactions between bose-fermi and bose-bose particles. Such a system can be realized in current experiments with ultracold bose-fermi mixtures.We apply the Bethe-ansatz technique to find the exact ground state energy at zero temperature for any value of interaction strength and density ratio between bosons and fermions. We use it to prove the absence of the...

Source: http://arxiv.org/abs/cond-mat/0510801v2

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Jun 30, 2018
06/18

by
David Benjamin; Eugene Demler

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We study degenerate mixtures of "heavy" bosons and "light" superfluid bosons using a variational polaron transformation. We consider the Mott insulator-superfluid transition of the heavy species and find that at $T=0$ interaction favors the superfluid phase of the heavy species. Our analytic results agree well with numerically exact quantum Monte Carlo simulations in two dimensions. We then show that in three dimensions the variational polaron transformation can be combined...

Topics: Quantum Gases, Statistical Mechanics, Condensed Matter

Source: http://arxiv.org/abs/1401.0311

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Sep 22, 2013
09/13

by
Subir Sachdev; Eugene Demler

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We extend recent low temperature analyses of competing orders in the cuprate superconductors to the pseudogap regime where all orders are fluctuating. A universal continuum limit of a classical Ginzburg-Landau functional is used to characterize fluctuations of the superconducting order: this describes the crossover from Gaussian fluctuations at high temperatures to the vortex-binding physics near the onset of global phase coherence. These fluctuations induce affiliated corrections in the...

Source: http://arxiv.org/abs/cond-mat/0308024v3

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Sep 23, 2013
09/13

by
Daniel Podolsky; Eugene Demler

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A spin nematic is a state which breaks spin SU(2) symmetry while preserving translational and time reversal symmetries. Spin nematic order can arise naturally from charge fluctuations of a spin stripe state. Focusing on the possible existence of such a state in strongly correlated electron systems, we build a nematic wave function starting from a t-J type model. The nematic is a spin-two operator, and therefore does not couple directly to neutrons. However, we show that neutron scattering and...

Source: http://arxiv.org/abs/cond-mat/0411159v2

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Sep 18, 2013
09/13

by
Mehrtash Babadi; Eugene Demler

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We study the collective excitations of polarized single-component quasi-two-dimensional dipolar fermions in an isotropic harmonic trap by solving the collisional Boltzmann-Vlasov (CBV) equation. We study the response to both monopole and quadrupole perturbations of the trap potential and investigate the character of excitations in each case. Simple analytic formulas are provided based on the linearized scaling ansatz and accurate numerical results are obtained by satisfying the first eight...

Source: http://arxiv.org/abs/1209.3863v1

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1.5K

Feb 16, 2007
02/07

by
Demler, Christian Wilhelm

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Includes bibliographical references and index

Topic: Pastoral theology

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Sep 18, 2013
09/13

by
Eugene Demler; Shou-Cheng Zhang

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We review the explanation for resonant neutron scattering experiments in $YBa_2Cu_3O_{6+\delta}$ and $Bi_2 Sr_2 Ca_2 O_{8+\delta}$ materials from the point of view of triplet excitation in the particle-particle channel, the pi excitation. Relation of these resonances to the superconducting condensation energy and their role in stabilizing the superconducting state is discussed. Due to the superconducting fluctuations, the pi resonance may appear as a broad peak above Tc. Analogue problem to the...

Source: http://arxiv.org/abs/cond-mat/9903195v1

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Sep 18, 2013
09/13

by
Eugene Demler; S. Das Sarma

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We develop an effective spin theory to describe magnetic properties of the $\nu=2$ Quantum Hall bilayer systems. In the absence of disorder this theory gives quantitative agreement with the results of microscopic Hartree-Fock calculations, and for finite disorder it predicts the existence of a novel spin Bose glass phase. The Bose glass is characterized by the presence of domains of canted antiferromagnetic phase with zero average antiferromagnetic order and short range mean antiferromagnetic...

Source: http://arxiv.org/abs/cond-mat/9811047v1

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Sep 20, 2013
09/13

by
C. J. Bolech; Eugene Demler

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The zero-energy bound states at the edges or vortex cores of chiral p-wave superconductors should behave like majorana fermions. We introduce a model Hamiltonian that describes the tunnelling process when electrons are injected into such states. Using a non-equilibrium green function formalism, we find exact analytic expressions for the tunnelling current and noise and identify experimental signatures of the majorana nature of the bound states to be found in the shot noise. We discuss the...

Source: http://arxiv.org/abs/cond-mat/0607779v2

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Jul 20, 2013
07/13

by
Sankar Das Sarma; Eugene Demler

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We discuss and review recent advances in our understaning of quantum Hall systems where additional quantum numbers associated with spin and/or layer (pseudospin) indices play crucial roles in creating exotic quantum phases. Among the novel quantum phases we discuss are the recently discovered canted antiferromagnetic phase, the spontaneous interlayer coherent phase, and various spin Bose glass phases. We describe the theoretical models used in studying these novel phases and the various...

Source: http://arxiv.org/abs/cond-mat/0009372v1

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Sep 22, 2013
09/13

by
Daw-Wei Wang; Eugene Demler

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We analyze theoretically the collective mode dispersion in multi-layer stacks of two dimensional dipolar condensates and find a strong enhancement of the roton instability. We discuss the interplay between the dynamical instability and roton softening for moving condensates. We use our results to analyze the decoherence rate of Bloch oscillations for systems in which the s-wave scattering length is tuned close to zero using Feshbach resonance. Our results are in qualitative agreement with...

Source: http://arxiv.org/abs/0812.1838v1

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Sep 21, 2013
09/13

by
R. W. Cherng; E. Demler

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We study periodic crystalline spin textures in spinor condensates with dipolar interactions via a systematic symmetry analysis of the low-energy effective theory. By considering symmetry operations which combine real and spin space operations, we classify symmetry groups consistent with non-trivial experimental and theoretical constraints. Minimizing the energy within each symmetry class allows us to explore possible ground states.

Source: http://arxiv.org/abs/1008.2240v1

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Jul 22, 2013
07/13

by
Ari M. Turner; Eugene Demler

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Condensates of atoms with spins can have vortices of several types; these are related to the symmetry group of the atoms' ground state. We discuss how, when a condensate is placed in a small magnetic field that breaks the spin symmetry, these vortices may form bound states. Using symmetry classification of vortex-charge and rough estimates for vortex interactions, one can show that some configurations that are stable at zero temperature can decay at finite temperatures by crossing over energy...

Source: http://arxiv.org/abs/0807.4905v1

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Jul 20, 2013
07/13

by
R. W. Cherng; Eugene Demler

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We consider the use of quantum noise to characterize many-body states of spin systems realized with ultracold atomic systems. These systems offer a wealth of experimental techniques for realizing strongly interacting many-body states in a regime with a large but not macroscropic number of atoms where fluctuations of an observable such as the magnetization are discernable compared to the mean value. The full distribution function is experimentally relevant and encodes high order correlation...

Source: http://arxiv.org/abs/cond-mat/0609748v2

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Sep 22, 2013
09/13

by
Eugene Demler; Shou-Cheng Zhang

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In this work we investigate properties of fermions in the SO(5) theory of high Tc superconductivity. We show that the adiabatic time evolution of a SO(5) superspin vector leads to a non-Abelian SU(2) holonomy of the SO(5) spinor states. Physically, this non-trivial holonomy arises from the non-zero overlap between the SDW and BCS quasi-particle states. While the usual Berry's phase of a SO(3) spinor is described by a Dirac magnetic monopole at the degeneracy point, the non-Abelian holonomy of a...

Source: http://arxiv.org/abs/cond-mat/9805404v3

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Sep 20, 2013
09/13

by
E. Demler; A. M. Tsvelik

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It is shown that excitation spectra of Generalized Gibbs Ensembles (GGE) of one-dimensional integrable models with isotopic symmetry contain universal features insensitive to details of the distribution. Namely, the low energy limit of the subsystem of isotopic (for instance, spin) excitations is described by the effective action of a ferromagnet at thermodynamic equilibrium with a single temperature and with the stiffness determined by the initial conditions. The condition of universality is...

Source: http://arxiv.org/abs/1205.5491v3

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Sep 21, 2013
09/13

by
R. W. Cherng; E. Demler

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We study the low-energy effective theory of spinor condensate ferromagnets for the superfluid velocity and magnetization degrees of freedom. This effective theory describes the competition between spin stiffness and a long-ranged interaction between skyrmions, topological objects familiar from the theory of ordinary ferromagnets. We find exact solutions to the non-linear equations of motion describing neutral configurations of skyrmions and anti-skyrmions. These analytical solutions provide a...

Source: http://arxiv.org/abs/1008.2239v1

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Sep 19, 2013
09/13

by
Dirk K. Morr; Eugene Demler

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We present an {\it exact} quantum theory for the bound states in the vicinity of an edge or a line of impurities in a $d_{x^2-y^2}$ superconductor. For a (110)-surface we show that a finite dispersion of the one dimensional band of bound states leads to a two peak structure in the density of states (DOS). We study the effect of an applied magnetic field and a subdominant $id_{xy}$ order parameter on the DOS and discuss the implications of our results for tunneling experiments.

Source: http://arxiv.org/abs/cond-mat/0010460v1

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Sep 21, 2013
09/13

by
Dmitry A. Abanin; Eugene Demler

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Entanglement entropy has become an important theoretical concept in condensed matter physics, because it provides a unique tool for characterizing quantum mechanical many-body phases and new kinds of quantum order. However, the experimental measurement of entanglement entropy in a many-body systems is widely believed to be unfeasible, owing to the nonlocal character of this quantity. Here, we propose a general method to measure the entanglement entropy. The method is based on a quantum switch...

Source: http://arxiv.org/abs/1204.2819v1

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Sep 23, 2013
09/13

by
Eugene Demler; Shou-Cheng Zhang

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Within the t-J model of copper-oxides, the condensation energy can be related to the change in the dynamical spin structure factor between the superconducting and the normal states. By analyzing previous experimental data, we show that the change associated with the resonant neutron scattering peak found in $YBa_2Cu_3O_7$ can quantitatively account for the condensation energy. We argue that this analysis suggests a microscopic mechanism for high Tc superconductivity.

Source: http://arxiv.org/abs/cond-mat/9806336v2

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38

Sep 18, 2013
09/13

by
R. W. Cherng; E. Demler

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Superfluids with a tendency towards periodic crystalline order have both a phonon and roton like spectrum of collective modes. The softening of the roton spectrum provides one route to a supersolid. We show that roton softening occurs in 87Rb spinor condensates once dipolar interactions and spin dynamics are taken into account. By including the effects of a quasi-two-dimensional geometry and rapid Larmor precession, we show a dynamical instability develops in the collective mode spectrum at...

Source: http://arxiv.org/abs/0806.1991v1

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Sep 21, 2013
09/13

by
A. A. Burkov; Eugene Demler

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We show that vortices, induced in cold atom superfluids in optical lattices, may order in a novel vortex-Peierls ground state. In such a state vortices do not form a simple lattice but arrange themselves in clusters, within which the vortices are partially delocalized, tunneling between classically degenerate configurations. We demonstrate that this exotic quantum many-body state is selected by an order-from-disorder mechanism for a special combination of the vortex filling and lattice geometry...

Source: http://arxiv.org/abs/cond-mat/0602278v3

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Sep 21, 2013
09/13

by
Jay D. Sau; Eugene Demler

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Spin-orbit coupled superconductors are potentially interesting candidates for realizing topological and potentially non-Abelian states with Majorana Fermions. We argue that time-reversal broken spin-orbit coupled superconductors generically can be characterized as having sub-gap states that are bound to localized non-magnetic impurities. Such bound states, which are referred to as Shiba states, can be detected as sharp resonances in the tunneling spectrum of the spin-orbit coupled...

Source: http://arxiv.org/abs/1204.2537v2

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0.0

Jun 30, 2018
06/18

by
Johannes Bauer; Mehrtash Babadi; Eugene Demler

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We study the dynamics of magnetic correlations in the half-filled fermionic Hubbard model following a fast ramp of the repulsive interaction. We use Schwinger-Keldysh self-consistent second-order perturbation theory to investigate the evolution of single-particle Green's functions and solve the non-equilibrium Bethe-Salpeter equation to study the dynamics of magnetic correlations. This approach gives us new insights into the interplay between single-particle relaxation dynamics and the growth...

Topics: Quantum Gases, Other Condensed Matter, Strongly Correlated Electrons, Statistical Mechanics,...

Source: http://arxiv.org/abs/1411.4049

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Sep 21, 2013
09/13

by
Ryan Barnett; Eugene Demler; Efthimios Kaxiras

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We perform a detailed analysis of the band structure, phonon dispersion, and electron-phonon coupling of three types of small-radius carbon nanotubes (CNTs): (5,0), (6,0), and (5,5) with diameters 3.9, 4.7, and 6.8 \AA respectively. The large curvature of the (5,0) CNTs makes them metallic with a large density of states at the Fermi energy. The density of states is also strongly enhanced for the (6,0) CNTs compared to the results obtained from the zone-folding method. For the (5,5) CNTs the...

Source: http://arxiv.org/abs/cond-mat/0407644v1

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Sep 22, 2013
09/13

by
Y. Bazaliy; E. Demler; S. C. Zhang

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A recent theory of the resonant neutron scattering peaks in YBCO superconductors predicts the existence of a sharp spin triplet two particle collective mode (the ``\pi resonance") in the normal state. In this paper, we propose an experiment in which the \pi resonance could be probed directly in a two particle tunneling measurement.

Source: http://arxiv.org/abs/cond-mat/9704022v1

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Sep 17, 2013
09/13

by
Vladimir Gritsev; Peter Barmettler; Eugene Demler

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Understanding non-equilibrium quantum dynamics of many-body systems is one of the most challenging problems in modern theoretical physics. While numerous approximate and exact solutions exist for systems in equilibrium, examples of non-equilibrium dynamics of many-body systems, which allow reliable theoretical analysis, are few and far between. In this paper we discuss a broad class of time-dependent interacting systems subject to external linear and parabolic potentials, for which the...

Source: http://arxiv.org/abs/0912.2744v3

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Sep 22, 2013
09/13

by
David Pekker; Rajdeep Sensarma; Eugene Demler

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We propose a pump probe experiment for detecting the d-wave superfluid and d-density wave phases of ultracold Fermions on an optical lattice. The pump consists of periodic modulations of the optical lattice intensity which creates quasiparticle pairs in these systems. The changes in the momentum distribution under the drive can be used to measure quasiparticle dispersion and gap anisotropy. Further, we show that the pattern of peaks and dips in the spin selective density-density correlation...

Source: http://arxiv.org/abs/0906.0931v1

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Sep 24, 2013
09/13

by
Eugene Demler; Subir Sachdev; Ying Zhang

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We argue that recent neutron scattering measurements by Lake et. al. (Science 291, 1759 (2001)) of the spin excitation spectrum of LSCO in a magnetic field can be understood in terms of proximity to a phase with co-existing superconductivity and spin density wave order. We present a general theory for such quantum transitions, and argue that their low energy spin fluctuations are controlled by a singular correction from the superflow kinetic energy, acting in the region outside the vortex...

Source: http://arxiv.org/abs/cond-mat/0103192v4

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0.0

Jun 30, 2018
06/18

by
Sarang Gopalakrishnan; Colin V. Parker; Eugene Demler

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A magnetic impurity in a fermionic superfluid hosts bound quasiparticle states known as Yu-Shiba-Rusinov (YSR) states. We argue here that, if the impurity is mobile (i.e., has a finite mass), the impurity and its bound YSR quasiparticle move together as a midgap molecule, which has an unusual "Mexican-hat" dispersion that is tunable via the fermion density. We map out the impurity dispersion, which consists of an "atomic" branch (in which the impurity is dressed by...

Topics: Quantum Gases, Superconductivity, Quantum Physics, Mesoscale and Nanoscale Physics, Condensed Matter

Source: http://arxiv.org/abs/1405.6717

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Sep 19, 2013
09/13

by
Vladimir Gritsev; Anatoli Polkovnikov; Eugene Demler

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We use quantum sine-Gordon model to describe the low energy dynamics of a pair of coupled one-dimensional condensates of interacting atoms. We show that the nontrivial excitation spectrum of the quantum sine-Gordon model, which includes soliton and breather excitations, can be observed in experiments with time-dependent modulation of the tunneling amplitude, potential difference between condensates, or phase of tunneling amplitude. We use the form-factor approach to compute structure factors...

Source: http://arxiv.org/abs/cond-mat/0701421v1

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Sep 21, 2013
09/13

by
V. Gritsev; E. Demler; A. Polkovnikov

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We propose a new method for detecting paired states in either bosonic or fermionic systems using interference experiments with independent or weakly coupled low dimensional systems. We demonstrate that our method can be used to detect both the FFLO and the d-wave paired states of fermions, as well as quasicondensates of singlet pairs for polar F=1 atoms in two dimensional systems. We discuss how this method can be used to perform phase-sensitive determination of the symmetry of the pairing...

Source: http://arxiv.org/abs/0808.0499v1

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Sep 20, 2013
09/13

by
Adilet Imambekov; Vladimir Gritsev; Eugene Demler

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We introduce a new class of sine-Gordon models, for which interaction term is present in a region different from the domain over which quadratic part is defined. We develop a novel non-perturbative approach for calculating partition functions of such models, which relies on mapping them to statistical properties of random surfaces. As a specific application of our method, we consider the problem of calculating the amplitude of interference fringes in experiments with two independent low...

Source: http://arxiv.org/abs/cond-mat/0612011v3

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4.0

Jun 27, 2018
06/18

by
Mehrtash Babadi; Eugene Demler; Michael Knap

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We study theoretically the far-from-equilibrium relaxation dynamics of spin spiral states in the three dimensional isotropic Heisenberg model. The investigated problem serves as an archetype for understanding quantum dynamics of isolated many-body systems in the vicinity of a spontaneously broken continuous symmetry. We present a field-theoretical formalism that systematically improves on mean-field for describing the real-time quantum dynamics of generic spin-1/2 systems. This is achieved by...

Topics: Condensed Matter, Quantum Physics, Strongly Correlated Electrons, Quantum Gases

Source: http://arxiv.org/abs/1504.05956

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Sep 23, 2013
09/13

by
Anatoli Polkovnikov; Ehud Altman; Eugene Demler

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We consider a problem of interference between two independent condensates, which lack true long range order. We show that their interference pattern contains information about correlation functions within each condensate. As an example we analyze the interference between a pair of one dimensional interacting Bose liquids. We find universal scaling of the average fringe contrast with system size and temperature that depends only on the Luttinger parameter. Moreover the full distribution of the...

Source: http://arxiv.org/abs/cond-mat/0511675v2

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Sep 20, 2013
09/13

by
Timofey Rostunov; Antoine Georges; Eugene Demler

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We discuss collective spin wave excitations in triplet superconductors with an easy axis anisotropy for the order parameter. Using a microscopic model for interacting electrons we estimate the frequency of such excitations in Bechgaard salts and ruthenate superconductors to be one and twenty GHz respectively. We introduce an effective bosonic model to describe spin-wave excitations and calculate their contribution to the nuclear spin lattice relaxation rate. We find that in the experimentally...

Source: http://arxiv.org/abs/cond-mat/0506548v1

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Sep 21, 2013
09/13

by
I. Zapata; F. Sols; E. Demler

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We show that triplet pairing correlations are generated in purely s-waves superfluids whenever population imbalance enforces anisotropic Fulde-Ferrell (FF) or inhomogeneous Larkin-Ovchinikov (LO) states. The same set of quasiparticle states contributes to the triplet component and to the polarization, thus spatially correlating them. In the LO case, this set forms a narrow band of Andreev states centered on the nodes of the s-wave order parameter. This picture naturally provides a unifying...

Source: http://arxiv.org/abs/1106.1605v2

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Sep 18, 2013
09/13

by
L. Brey; E. Demler; S. Das Sarma

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We make a number of precise experimental predictions for observing the various magnetic phases and the quantum phase transitions between them in the $\nu$=2 bilayer quantum Ha ll system. In particular, we analyze the effect of an external bias voltage on the quantum phase diagram, finding that a finite bias should readily enable the experimental observation of the recently predicted novel canted antiferromagnetic phase in transport and spin polarization measurements.

Source: http://arxiv.org/abs/cond-mat/9901296v1

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37

Sep 23, 2013
09/13

by
Andreas Wagner; Christoph Bruder; Eugene Demler

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We examine spinor Bose-Einstein condensates in optical superlattices theoretically using a Bose-Hubbard Hamiltonian that takes spin effects into account. Assuming that a small number of spin-1 bosons is loaded in an optical potential, we study single-particle tunneling that occurs when one lattice site is ramped up relative to a neighboring site. Spin-dependent effects modify the tunneling events in a qualitative and quantitative way. Depending on the asymmetry of the double well different...

Source: http://arxiv.org/abs/1110.1968v2

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26

Sep 18, 2013
09/13

by
R. W. Cherng; Gil Refael; Eugene Demler

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We study the interplay between superfluidity and magnetism in a multicomponent gas of ultracold fermions. Ward-Takahashi identities constrain possible mean-field states describing order parameters for both pairing and magnetization. The structure of global phase diagrams arises from competition among these states as functions of anisotropies in chemical potential, density, or interactions. They exhibit first and second order phase transition as well as multicritical points, metastability...

Source: http://arxiv.org/abs/0705.0347v1